Spark-plug.



No. 868,737. PATENTED OCT. 22, 1907. F. J. WATT. SPARK PLUG.

APPLIOA'I'IOI nun n11. as. 1004.

IN VEJV' T OR.

WNWESSES.

UNITED STATES PATENT OFFICE.

FRANK J. WATT, or DETROIT, MICHIGAN, ASSIGNOR OF ONE-HALF TO ROY n. HARDY, 0F N W YORK, N. Y.

SPARK-PLUG.

Specification of Letters Patent.

Patented Oct. 22, 1607.

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devices for explosive engines, known as jump spark igniters and refers more particularly to spark plugs for such igniters. v The object of the invention is to provide a spark plug so constructed as to perfectly insulate .the electrodes and obviate the danger of shortcircuiting by reason of the accumulation of the products of combustion etc., and also so constructed that no adjusting of the points is necessary in assembling and the distance between the points will not be changed by the turning of either.

A further object of the invention is to provide means whereby the parts, while, being firmly held, are allowed to expand and contract relative to each other and whereby the breaking of the insulation is thus prevented, and it is also an object of the invention to so construct and arrange the plug that the sparking points will be protectedagainst accidental breaking or displacement in handling when the plug is not in use, and to provide certain other new and useful features, all as hereinafter more fully described and shown in the accompanying drawings, in which:

Figure 1,- is a side elevation of a device embodying the invention; Fig. 2, a longitudinal section of the same; and Fig. 3, an elevation of the lower or inner end thereof.-

A is a steel bushing or shell externally screw-threaded and provided with a hexagonal head by means of which it is turned into a suitable screw-threaded opening in the cylinder wall or head. This bushing is provided with a central chamber or bore A which is reduced in loosely within the reduced bore of the bushing and is formed intermediate its ends with a shoulder B to 0ppose the shoulder A of the bushing. The insulating plug B is also formed with a longitudinal axial bore 13 through which loosely panes a binding bolt 0 provided with a. head or nut C at its inner end to engage the inner end of the plug and screw-threaded at its opposite end to receive a nut C to engage the opposite end of the plug. Interposed between the shoulder on the plug and the shoulder on the bushing is an asbestos packi \g ring D and a porcelain insulating cap E provided'with an opening through which the bolt 0 passes, sits loosely over and incloses the end of the plug which projects through the bushing and rests on the outer end of said bushing, the plug. being drawn into contactwith the packing by a nut F on the outer end of the bolt which engages a washer G interposed between the nut F and the end of the cap which cap is also held in place by said nut. The washer G is bent transversely'so that when the'parts contract or expand the washer will spring slightly and thus take the strain off the insulation and prevent it being cracked thereby A look nut F is provided on the bolt in engagement with the nut F toprevent the same from coming loose and on the extreme outer end'of the bolt is a binding nut F to bind the wire conductor to the bolt, which bolt serves as one electrode, the bushing A serving as the other electrode. The porcelain cap E prevents water coming in contact with the heated plug B and cracking it-and I is an asbestos ring packing preferably placed between the bushing B and captoallow the porcelain cap to have a more even temperature. If another spring or asbestos washe. maybe interposed between the nut C and porcelain plugB.

' The bolt or electrode C may be'formed with a C or provided with a nut to form a head thereon, and

the head is bored inward at one side and into this hole is driven a short platinum wire which projects outward toward the bushing and forms a sparking point H.- The sparking point extends outward from the head C just inside the end of the bushing and therefore will not be bent orbroken in handling the plug before it is attached to the engine cylinder. By using the inner end of the bushing as the other sparking point the points arealways at the proper distance from each other, no matter how the parts are turned, and no-adjusting of the points is required to bring them at the proper distance from each other.

Having thus fully described my invention, what I claim is:

1. In a spark plug, the combination 0! an xternally screw-threaded bushing provided with a cent bore re duced in diameter near its upper end to form a shonlden.

engage' the inner end of the plug, a sparking point se-' cured to said head and extending laterally therefrom toward and within the inner face of the wall of the bushing, -a nut on the bolt engaging the opposilte end of the plug,

an insulating cap having an opening for the passage of the bolt inclosing the outer end of the plug and seated upon the end of the bushing, a packing ring interposed tie-p tween the cap and bushing, a washer bent to form a spring sleeved on the bolt in engagement with the cap, and 'a nut and binding nut to engage said washer and clamp the parts together.

Y 2. In a spark plug, the combination with an externally screw-threaded metal bushing forming an electrode and an insulating plug of a diameter to pass partially through provided with anfaxial internal-bore forrned with a shoul- (10?. :1 porcelain insulating plug formed with an annular shoulder lntermedlate, itsen'ds to oppose the shoulder on,

the bushing and having an axial bore ofunlform diameter, an asbestos packing ring interposed between said slieulders, i1 porcelain insulating cap inclosing the outer end of the'piug and engaging the outer end of the bushing, an

extending laterally therefrom within the bushing, a' nut j Witnesses:

on the bolt engaging the opposite end of the plug, a second nut on the outer end of said bolt, a' spring washer interposed between said nut and cap to allow for the unequal expansion of the parts and a lock anda binding nut on said bolt. 4 V

In testimony whereof I atiix my signature in presence of two witnesses FRANK L1. WATT.

OTTO 1 BARTHEL, THOMAS G. LONG-STAFF. 

